Practice passage
The domestication of the horse is among the most consequential events in human prehistory, and among the hardest to date. Unlike pottery or metalwork, the practice leaves few objects behind. A domesticated horse and a hunted one produce much the same bones, and the equipment used to control early horses was made of rope and leather, materials that rarely survive in the archaeological record. For most of the twentieth century, then, the question was argued from indirect evidence, and the estimates ranged across two thousand years.
Three lines of evidence have narrowed the range. The first is dental. A horse controlled by a bit develops a characteristic pattern of wear on the second premolar, where the metal or bone repeatedly strikes the tooth. Where this wear appears on excavated teeth, some form of riding or driving is a reasonable inference, though the wear can also be produced by other causes and a single worn tooth proves little on its own.
The second line is chemical. Residue analysis of pottery from settlement sites has identified the fatty acids characteristic of mare's milk. Milking implies a herd managed closely enough to be milked, which is a considerably stronger claim than proximity, and it implies a relationship maintained across generations rather than a single captured animal.
The third and most decisive line is genetic. Sequencing of ancient horse remains has shown that the modern domestic horse descends from a population that expanded rapidly from a limited region, replacing other lineages across the continent within a few centuries. The speed of that replacement is itself the evidence: a wild population does not spread that way, but a useful animal carried by people does.
Taken together these lines converge on a narrower window than any one of them supports alone, which is the ordinary condition of prehistoric dating. No single find settles the question. What changes the estimate is the accumulation of independent methods that happen to agree, and the corresponding difficulty of explaining that agreement any other way.